Electric lamp



Jan. 18,1938.

J. BERGMANS ELECTRIC LAMP Filed July 15, 1935 2 Sheets-Sheet 1 Main plane Inventor:

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Auxiliary plane J. BERGMANS Jan. 18, 1938.

ELECTRIC LAMP Filed July 15, 1935 2 Sheets-Sheet 2 Auxilia rpiome Fig.5.

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His Attorney.

Patented Jan. l8,

UNITED STATES PATENT oar-"ice to General Electric New York Company, a corporation of Application m, is, 1935, Serial No. 31,486 In the Netherlands July as, 1934 7 Claims.

My invention relates to electric lamps and more degrees. This plane will be referred to hereinafter as the main plane. The vertex angle of the cone measured in a second vertical plane at.

right angles to the main plane and passing through the transverse axis of the base and through the center of the bulb, has a maximum value of '75 degrees. This plane will be referred to hereinafter as the auxiliary plane.

For a further understanding of the invention, reference may be had to the drawings in which Fig. 1 is a perspective view of an incandescent lamp comprising my invention; Fig. 2 is 9. diagrammatic section through the bulb in the main plane and at right angles to the longitudinal axis of the lamp seen in Fig. 1; Fig. 3 is a bottom view of the lamp; Fig. 4 is a. perspective representation of the sub-conical light beam. emitted by the lamp; Fig. 5 is a. representation of the light intensity of the reflected beam in the main plane; and Fig. 6 is a similar representation for the auxiliary plane at enlarged scale.

Referring ,to Figs. 1 to 3, the lamp comprises a bulb it having a base ll attached thereto. The neck of the bulb with the base attached thereto is shown in the drawings as being in the longitudinal axis of the bulb, but it may be located at some other part if desired. The upper part of the bulb is provided with a reflecting surface M, such as a silver coating on the inner or outer surface thereof. The shape of the bulb is such that the curvature of cross-sections of the reflecting part of the bulb in planes which are perpendicular to the main plane and pass through the center of the filament, or through the longitudinal axis of the bulb, increases as the auxiliary plane is approached.

Referring to Fig. 2, the cross-section of the reflecting part of the bulb in the main plane comprises two parabolic side portions AB and CD which extend over a. sector angle of 30 to 40 degre'es. The lines AD and CB are the axes of these portions CD and AB respectively. The intermediate portion AEC of the said section of the reflecting surface increases in curvature as the auxiliary plane is approached, that is, the distance from the center M of the bulb to the bulb wall increases as the top E of the bulb is approached. (The distance ME is greater than the distance MA.)

The filament is preferably located at the center of the bulb. If the filament can be so concentrated that its length is approximately 0.15 times the length of the bulb axis, then it may be disposed in said axis. However, if this is not possible, the filament is preferably disposed in the main plane perpendicular to the line of.intersection of the main and auxiliary planes, in which case the filament is made linear or v-shaped. In the latter case, the legs of theV-shaped filament are preferably located in the axes of the parabolic portions of the bulb to prevent the light emitted directly by the filament from having a blinding efiect. I

The filament l3 shown in the drawings is V- shaped and is located in the main plane so that the apex of the filament faces the transpment ribs or flutes H or with other difiusing means in order to obtain a more uniform light.

Fig. 4 shows the reflected sub-conical beam which is emitted by the lamp, the base K on the plane V being elongated. The vertex angle of the cross-section of the beam in the main plane has a maximum value of 160 degrees. The vertex angle of the cross-section of the beam in the auxiliary plane has a maximum value of '15 degrees.

Figs. 5 and 6 illustrate the light intensities of the beam in the main and auxiliary planes respectively. In the main plane, as shown in Fig. 5, the intensity of the light increases toward the outer edge of thebeam, while in the auxiliary plane, as shown in Fig. 6, the intensity is substantially uniform.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric lamp comprising a. bulb having increasing curvature as the sections are taken in planes approaching the'middle of said reflecting portion from its sides, and a light source located within said reflecting bulb portion.

2. 'An electric lamp comprising a bulb having an elongated concave light-deflecting portion so shaped that cross-sections thereof in planes passing through the longitudinal axis thereof are of increasing curvature as the sections are taken in planes approaching-the middle 01' said reflecting portion from its sides, the cross-section of said reflecting bulb portion at the middle thereof in a plane transverse to said longitudinal axis comprising parabolic side portions and'an intermedi ate portion of increasing curvature from the sides to the middle, and a light source located within said reflecting bulb portion.

3. An electric lamp comprising a bulb having an elongated concave light-reflecting portion, the

cross-section at the middle thereof in a plane transverse to the longitudinal axis comprising parabolic side portions and an intermediate portion of increasing curvature from the sides to its middle, and a light source located within said reflecting bulb portion.

4. An electric lamp comprising a bulb having planes approaching the middle of said reflecting portion from its sides, the cross-section of said reflecting bulb portion at the middle thereof in a plane transverse to said longitudinal axis comprising parabolic side portions and an intermediparabolic side portions and an intermediate portion of increasing curvature from the sides to its middle, and a V-shaped filament located at the middle of said reflecting bulb portion in a plane transverse to the longitudinal axis and with its leg portions extending toward the said concave reflecting bulb portion along the axes of the said parabolic side portions.

7. An electric lamp comprising a bulb having 7 an elongated concave light-reflecting portion so shaped that cross-sections thereof in planes passing through the longitudinal axis thereof are of increasing curvature as the sectionsare taken in planes approaching the middle of said reflecting portion from its sides, the cross-section of said reflecting bulb portion at the middle thereof in a plane transverse to said longitudinal axis comprising parabolic side portions ,and an intermediate portion of increasing" curvature from the sides to the middle, and a V-shaped fllament located at the middle of said reflecting bulb portion in a plane transverse to the longitudinal axis and with its leg portions extending toward the said concave reflecting bulb portion along the axes of the said parabolic side portions.

JAN BERGMANS. 

